Geared hub with freewheel, especially for wheel-chairs

ABSTRACT

A geared hub for wheelchairs is specified, which besides at least one forward speed has an active hub brake and one reverse speed, and in which the braking and/or the reverse speed can be realized, from any of the forward speeds, through turning the driver backwards.

DESCRIPTION

The invention refers to a geared hub with a freewheel, especially forwheelchairs, containing: a hub axle and a driver supported on the hubaxle, a hub sleeve supported at one side on the driver and at the otherside on a rotatable lever-cone, where the lever-cone may be fastened tothe frame of the vehicle by means of a brake lever, an epicyclic gearaccommodated within the hub sleeve, a coupling sleeve connecting thedriver to the ring gear or to the pinion cage of the epicyclic gear, athread on the pinion cage, onto which a brake cone may be screwedaxially and upon turning the driver backwards spreads a brake memberagainst the hub sleeve, at least one first ratchet gear havingspring-loaded pawls for the transmission of the driving torqueintroduced by the driver via the members of the epicyclic gear into thehub sleeve in the forwards direction of rotation.

From West German O/S No. 24 39 332, West German O/S No. 25 56 029, theWest German Patent No. 21 59 770 and West German O/S No. 25 14 418geared hubs of that kind are known. These known hubs are bicycle hubsand have a freewheel which enables the hub sleeve to be turned forwardsfreely relatively to the driver. Furthermore, these known hubs also havea back-pedal brake by means of which via a brake cone and a brakingmember braking forces are exerted from the inside upon the hub sleeve,when the driver gets turned back by a predetermined amount relatively tothe hub axle fastened to the vehicle frame, until the brake is applied.The epicyclic gear serves in the case of the known geared hubs forrealizing different gear ratios between the driver and the hub sleeve.Through axial shifting of the coupling sleeve which acts between thedriver and the members of the epicyclic gear or respectively throughaxial shifting of the members of the epicyclic gear the different gearratios may, in a known manner, be selectively produced.

This known hub is unsuitable for incorporation into wheelchairs since,corresponding with its application to bicycles, it does not allowdriving the hub sleeve in the backwards direction. Furthermore, theseknown hubs all have unblocking mechanisms which ensure release of thebrake under all circumstances. In order to make this possible, theseunblocking mechanisms produce a relatively large rotary play of from 20°to 40° in the forwards direction between the driver and the hub sleeve.This rotary play ensures that, with the backpedal brake fully braked,the brake cone is first withdrawn and the braking member therebyreleased, and that only after that does the ratchet gear acting betweenthe driver and the hub sleeve take the hub sleeve with it again solidlyin the forwards direction. Due to the construction this rotary playbetween the driver and the hub sleeve also exists in the case of theknown hubs when the driver is to drive the previously freewheeling hubsleeve once again in the forwards direction via the correspondingratchet gear.

Since the known hubs do not allow any driving in the backwards directionand since furthermore a rotary play of about 20° to 40° must always beovercome, if the driver wants to exert upon the previously freewheelinghub sleeve a driving torque, this known hub cannot be used inwheelchairs.

From West German O/S No. 26 29 839 a special wheelchair hub is furtherknown which has a freewheel mechanism. From West German O/S No. 32 41614 a wheelchair is likewise known which can be actuated by means of ahand lever and has a freewheel coupling. The hubs of these knownwheelchairs do not have any change-speed gearing and furthermore have noactive brake which can be actuated by the driver.

From West German O/S No. 29 29 138 a wheelchair is again known, whichhas a hub with a gear which, by selection, enables reversal of thedirection of rotation and furthermore exhibits gear ratios which may beselected. This known hub likewise has no backpedal brake which can beactivated by the driver.

By comparison, the problem of the invention is to develop a geared hubof the kind specified initially, further in such a way that a simpledrive in the forwards and in the backwards directions is possiblewithout essential rotary play or angular backlash between the driver andthe hub sleeve.

In the case of the geared hub of the kind specified initially thisproblem is solved in accordance with the invention by there beingprovided between the brake member and the brake lever or respectivelythe frame of the vehicle a second ratchet gear which freewheels if atorque in the backwards direction of rotation is transmitted from thedriver via the coupling sleeve, the members of the epicyclic gear, thebrake cone and the spread brake member to the hub sleeve.

If in the case of the hub, in accordance with the invention, the driveris turned back, relatively to the fixed hub axle, the pinion cage, viathe coupling sleeve and the epicyclic gear, likewise gets turned back,whereupon the brake cone travels along its thread axially towards thebake member and spreads the brake member against the hub sleeve andthereby brakes the hub sleeve. The braked rest position of the hubsleeve is thereby reached. If, from this braked position the dirver isnow turned further in the backwards direction the driver, via thecoupling sleeve and the epcicyclic gear and via the frictionalconnection of the activated brake, carries the hub sleeve with it in thebackwards direction because now the second ratchet gear freewheels sothat at least that part of the lever cone against which the brake memberbears, can turn with it in the backwards direction.

Thus, the hub, in accordance with the invention, makes it possiblethrough turning backwards the driver which in the case of a wheelchairis connected solidly to the handwheel rims, first to trigger thebackpedal brake, to bring the hub sleeve thereby to a standstill, andsubsequently through further turning backwards to take the hub sleevealong in the backwards direction via the frictional connection of theactivated brake. A wheelchair equipped with this hub can, therefore, bedriven by the handwheel rim in the forwards direction, in which case afreewheel is provided between the hub sleeve/running wheel and thedriver/handwheel. The backpedal brake may be activated during forwardsmotion or at standstill of the wheelchair. Through further turning ofthe driver backwards a backwards rotation of the hub sleeve/runningwheel then takes place.

If the hub sleeve gets braked from a forwards rotation, as a rule, heavybraking forces act between the hub sleeve and the spread braking member.If by chance upon reaching standstill just one pawl of the first ratchetgear now catches in the associated set of teeth, the strain imposed inthe case of the known geared hubs upon the hub sleeve, the first ratchetgear, the members of the epicyclic gear, the brake cone and the brakemember, which there may be eliminated only through additional unblockingmechanisms and corresponding angle of backlash/rotary play, iseffectively avoided in accordance with the invention through the factthat the driver may be turned back beyond the fully braked position.That is, upon turning the driver backwards again from standstill thepawls of the first ratchet gear are turned because of the gear ratio ofthe epicyclic gear more rapidly in the backwards direction than the hubsleeve which via the frictional engagement of the brake is coupledfirmly to the pinion cage. Thus, in accordance with the invention, uponturning the driver back, starting from standstill, the first ratchetgear freewheels and through this freewheeling prevents the strain uponor blocking of the brake.

Additional unblocking mechanisms which in the case of any forwardsturning or forwards driving motion of the driver effected relatively tothe hub sleeve create a large angle of backlash/rotary play and which,in the case of application in a wheelchair, would convert the availabledriving movement of the hands essentially into the angle ofbacklash/rotary play, can therefore be dispensed with. In accordancewith the invention, on the contrary, for the first ratchet gear aparticularly small tooth pitch t and/or a relatively larte number ofpawls may be arranged at differing spacing in order to limit theforwards angle of backlash preferably to a value between about 1° and6°. The user of a wheelchair who is driving his wheelchair via the hubin accordance with the invention by means of a handwheel rim fastened tothe driver, therefore has available for driving the wheelchairessentially the whole angle of rotation which can be covered each timehe takes a fresh grip.

The lever cone is advantageously subdivided into an outer part which canbe fixed to the frame of the wheelchair by means of the brake lever, andan inner rotatable part. The second ratchet gear is arranged between theouter and inner parts of the lever cone.

Alternatively, the second ratchet gear may also be inserted between thelever cone and the brake lever or respectively the frame of the vehicle.On the outside of the endface of the lever cone a gearwheel is thenmounted, which cooperates with a spring-loaded pawl which is fastened tothe brake lever and couples the brake cone to the brake lever whentorques are exerted upon the brake cone because of a braking procedure.In the backwards direction of rotation, on the contrary, the brake conethrows out of the pawl and freewheels.

It is particularly preferable that the first ratchet gear be arrangedbetween the ring gear of the epicyclic gear and the inner circumferenceof the hub sleeve. For reduction of the angle of backlash of the firstratchet gear a suitable number of spring-loaded pawls is fitted on theouter circumference of the ring gear of the epicyclic gear. Preferably,the circumferential spacing of the pawls from one another is unequal toa multiple of the pitch t of the associated toothed ring, whereby theangle of backlash is further reduced because, of course, the individualpawls at any instant are lying in different relative positions withrespect to the teeth of the toothed ring. Thus, while one pawl muststill cover the maximum angle of backlash until engagement in the nexttooth, another pawl or respectively another group of pawls is nearer thepoint of engagement. In order to achieve this action the pawls may alsohave circumferential spacings which differ from one another.

It is particularly preferable that the geared hub be provided with gearratios which may be selected. For this purpose, the coupling sleevewhich acts between the driver and the members of the epicyclic gear ismade able to shift axially and in a first position connects the driverto the ring gear (normal speed) and in a second position connects thedriver to the pinion cage (high speed). Furthermore, a third ratchetgear may be provided, which is arranged on the pinion cage and servesfor the realization of a third speed (hill speed) if, via the changespeed mechanism, the first ratchet gear is put out of action throughaxial shifting.

In accordance with the invention the geared hub is built intowheelchairs which have a frame and at least two running wheels at thesides and one handwheel each for driving the running wheels. The axle ofthe hub and the brake lever are fastened to the frame of the wheelchairso as to be unable to turn. The running wheels are fastened to the hubsleeve, and the handwheel rims to the driver.

Embodiments of the invention are explained in greater detail below withthe aid of the drawings, wherein:

FIG. 1 is a geared hub in accordance with the invention, half-sectionedlongitudinally;

FIG. 2 is a second embodiment of the invention, in section;

FIG. 3 is a section along the line III--III of FIG. 1; and

FIG. 4 is a second embodiment of the pawl wheel of FIG. 3.

On a fixed hub axle 1 are arranged on one side a driver 2 and on theother side a lever cone 3, upon which a hub sleeve 4 is supported to beable to rotate by means of ball bearings 5 and 6 respectively.

The driver 2 can via a permanently coupled axially displaceablesleeve-shaped coupling member 9 which in turn exhibits external sets ofcoupling teeth of various diameters, be connected at option to a pinioncage 10 exhibiting internal teeth or to the ring gear 14 of theepicyclic gear 10-14. The epicyclic gear comprises, moreover, apart fromthe pinion cage 10 which is able to turn on the hub axle 1, planetpinions 11 on axles 12 on the pinion cage, a sun wheel 13 fixed inrotation onto the hub axle 1 as well as the ring gear 14 which isconstantly in engagement with the planet pinions 11. On thesleeve-shaped shank of the pinion cage 10 a thread is arranged uponwhich a brake cone 17 is fitted to be able to screw axially, which uponturning the driver backwards shifts a brake member 27 axially towardsthe lever cone 3 and then spreads it outwards and forces it against thehub sleeve 4.

As a freewheel between the ring gear 14 and the hub sleeve 4 a firstratchet gear 15, 18 is fitted, which carries on a pawl wheel 15 pawls15c which are spring-loaded against an inner toothed ring 18 and catchin the internal set of teeth 18 for the transmission of the drivingtorque acting in the forwards direction of rotation, introduced by thedriver 2 via the epicyclic gear 10-14.

There is further provided a third ratchet gear 16, 19 the pawl of whichis arranged on the brake cone 17, from which spring-loaded pawls canengage in a set of internal teeth 19 in the hub 4 if a driving torque isto be transmitted in the forwards direction of rotation.

The geared hub illustrated has three different gear ratios which may beswitched in at option and are also designated "speeds". In FIG. 1, theswitching position "high speed" is illustrated, in which via thecoupling sleeve 9 which is supported to be able to rotate and to shiftaxially on the hub axle 1, the driver 2 is connected to the pinion cage10 which is able to rotate on the hub axle 1, so that in turn the pinioncage 10 drives via the planet pinions 11 the ring gear 14, that is, athigher r.p.m. so that the ratchet gear 15 on the ring gear 14 drives thehub sleeve via the internal set of teeth 18, while the ratchet gear 16lying on the slower turning brake cone 17 on the shank of the pinioncage 10 does not come into engagement with the associated internal setof teeth 19 in the hub sleeve 4 because the latter in consequence ofbeing driven via the faster running ring gear 14 revolves faster and forthe ratchet gear 16 a freewheeling state thereby arises.

Upon appropriate shifting of the coupling sleeve 9 towards the right inthe Figure, via a thrustblock not designated more precisely and byswitching rod and switching pullchain in the hollow-drilled hub axle, 1,the driving connection of the driver 2 via the coupling sleeve 9 to thepinion cage 10 is removed and instead of it the ring gear 14 is drivenby the coupling sleeve 9 through engagement of the set of coupling teethon the coupling sleeve 9 with the set of internal teeth 22 in the ringgear 14. The driving connection now goes from the driver 2 via thecoupling sleeve 9 directly into the ring gear 14 which in turn by theratchet gear 15, 18 drives the hub sleeve 4 in "normal speed".

The third possible switching position of the embodiment, that of the"hill speed" is obtained by the coupling sleeve 9 being shifted on thehub axle 1 still further towards the right by means of the aforesaidswitching pull members, that is, against the resilience of a compressionspring 20 into the bore in the driver 2. By this axial shifting of thecoupling sleeve 9 the ring gear 14 too is at the same time shiftedaxially against a compression spring 28 because a circlip 21 arranged togive a contracting grip on the coupling sleeve 9 strikes against the setof internal coupling teeth 22 on the ring gear 14 and then shifts thelatter likewise towards the right in the Figure by the same amount ofaxial shift of the coupling sleeve 9. During this axial shifting of thering gear 14 the engagement with the pinions 11 is preserved so that thepinion cage 10 may still be driven by the driver 2 via the couplingsleeve 9 and the directly coupled ring gear 14, but the pawls of theratchet gear 15 on the ring gear 14 get brought out of engagement withthe set of internal teeth 18 on the hub sleeve 4 by the pawls 14 uponaxial shifting of the ring gear 14 towards the right, coming into therange of a taper ring 24 the diameter of which in the hub sleevedecreases towards the right. The pawls of the ratchet gear 15 therebyget pressed radially inwards and thereby come out of engagement with theset of internal teeth 18. The transmission of the forwards drivingtorque is effected by the ring gear 14 which is driven only via thepinion cage 10 which is now turning slower and in turn drives the brakecone 17 with the pawls of the ratchet gear 16 lying on it, which nowproduces the connection to the hub sleeve 4 and drives the latter atslow speed.

The pinion cage 10 has on the end of it directed towards the lever cone3 a thread 10a upon which the brake cone 17 is supported to be able tobe screwed or shifted axially and acts by a taper face against a brakemember 27 when the driver 2 via the coupling sleeve 9 and if necessarythe ring gear 14 turns the pinion cage 10 in the backwards directionrelatively to the hub axle. The brake member 27 thereby, upon turningthe driver 2 backwards, comes with simultaneous bearing against thelever cone 3 into frictional engagement with the hub sleeve 4 whichthereby gets braked.

Between the brake member 27 and the brake lever 3a or respectively theframe of the vehicle a further ratchet gear 40, 42 is provided, whichfreewheels when a torque in the backwards direction is exerted upon thebrake member 27. For this purpose, in the embodiment illustrated in FIG.1, the lever cone 3 is subdivided into an outer part 3b which may befastened via the brake lever 3a to the frame of the vehicle, and arotatable inner part 3c which includes the bearing area for the brakemember 27. The ratchet gear 40, 42 has a pawl wheel 42 on the outer part3b of the lever cone, which carries pawls which are spring-loadedagainst a set of internal teeth on the part 3c and freewheel when therotatable inner part 3c of the lever cone experiences, via the brakemember 27, the brake cone 17, the pinion cage 10, the coupling sleeve 9and the driver 2, a torque in the backwards direction. If, on the otherhand, upon braking the hub sleeve 4 running in the forwards direction, atorque in the forwards direction is exerted via the brake member 27 uponthe part 3c of the lever cone 3, the ratchet gear 40, 42 couples thepart 3c solidly to the part 3b of the lever cone 3, which is fastened tothe frame of the vehicle. The part 3c of the lever cone and the brakemember 27 are coupled together by means of a coupling member 29 to beunable to twist apart.

In accordance with the embodiment of the invention illustrated in FIG.2, the ratchet gear 40, 42 is arranged between the brake lever 3a andthe brake cone 3 which is made in one piece. To the outer endface of thelever cone 3 is fatened a toothed ring 42 which cooperates with aspring-loaded pawl 40 which is fastened to the brake lever 3a. Theratchet gear 40, 42 freewheels when a torque in the backwards directionis introduced from the driver 2 via the spread brake member 27, but onthe other hand, it is blocked when, from the hub sleeve 4 turning in theforwards direction, a torque is introduced in the forwards directionfrom the activated brake member 27. The brake member 27 is coupled bymeans of the coupling member 29 to the lever cone 3 so that they cannottwist apart.

Hence, both the transmission hub in accordance with FIG. 1 and also thatin accordance with FIG. 2 have a number of forward speeds, an active hubbrake which may be activated by turning the driver backwards (backpedalbrake) and a reverse speed in which the ratchet gears 15, 18 and 16, 19freewheel and the drive is effected from the driver 2 via the couplingsleeve 9, the epicyclic gear 10-14, the brake cone 17, and the brakemember 27 via a frictional connection to the hub sleeve 4, the backwardsrotation only becoming possible because the further ratchet gear 40, 42then likewise freewheels.

FIG. 3 shows an embodiment of the pawl wheel 15 or 16 of the ratchetgears 15, 18 and 16, 19 respectively. In the embodiment shown the pawlseats 15b which receive the pawls 15c are arranged at differing spacingsfrom one another. The angle of backlash which must be covered until theengagement of a pawl 15c in one of the teeth of the set of internalteeth 18 is thereby reduced. Alternatively, the pawls 15c may bearranged equidistantly round the circumference, as shown in FIG. 4, inwhich case the number of teeth in the set of internal teeth 18 and thenumber of pawls 15c is so chosen that the spacings A of the pawls fromone another is unequal to a multiple of the pitch t of the set ofinternal teeth, i.e., that the equation to apply is A nt, where n=1, 2,3 . . . .

If at any time two pawls lying opposite one another are always to comesimultaneously into engagement with the set of of internal teeth 18, thecorresponding pairs of pawls are to be correspondingly offsetrespectively from adjacent pairs of pawls.

FIGS. 1 to 3 show geared hubs having three different gear ratios whichmay be set at option through switching members. But, alternatively, thegeared hub for use in wheelchairs may also be executed with merely onegear ratio of fixed setting. In this case, the driver 2 may be connectedsolidly via the coupling sleeve 9 to the pinion cage 10 or the ring gear14. The driver 2, coupling sleeve 9 and pinion cage 10 or respectivelyring gear 14 may then also be made in one piece. The ratchet gear 16, 19may then be omitted.

If the geared hubs in accordance with the invention are built intowheelchairs, as a rule, two hubs are arranged in axial alignment at apredetermined distance apart on the frame of the wheelchair with awheelchair seat between them. The hub axle 1 is bolted solidly to theframe and running wheels are fastened onto the hub sleeves 4 on oppositesides of the wheelchair seat. On each of the drivers 2 is seated ahandwheel rim having a diameter which is reduced as compared with therunning wheels in order to be able to drive the running wheels by hand.Wheelchairs of that kind have one or more forward speeds, a hub brakewhich, without having to release the handwheel rims, may be actuatedthrough turning the handwheel rims backwards, and a reverse speed whichis realized upon turning the handwheel rim backwards out of a forwardsmotion or standstill of the wheelchair after activation of hub brake.Hence, the user, without having to release the handwheel rims, canexecute all of the desired operations. In particular, an effectivebraking of the forward motion is possible and the user can furthermorechange over from a forward motion through an effective braking processdirectly into a backward motion or from a backward motion orrespectively from standstill into a forward motion without a very largeangle of backlash. And the user can, in particular, also perform aforward movement without noticeable angle of backlash between thehandwheel rims and the running wheel, whereby the angular rotationcovered by hand at any time is converted fully into a length of pathcovered.

What is claimed is:
 1. A geared hub with a freewheel adapted for usewith a wheelchair vehicle having a frame by which the hub is supported,containing:a hub axle and a driver supported on the hub axle; a hubsleeve supported at one side on the driver and at the other side on arotatable lever-cone, said lever-cone being mounted to the frame of thevehicle; an epicyclic gear having a pinion cage accommodated within thehub sleeve, a ring gear, a planet pinion and a braked sun gear; acoupling sleeve adapted to connect the driver alternatively to the ringgear or to the pinion cage of the epicyclic gear; a thread on the pinioncage having a brake cone screwed axially thereon which, upon turning thedriver backwards, spreads a brake member against the hub sleeve; atleast one first ratchet gear having a ratchet wheel and spring-loadedpawls for the transmission of the driving torque introduced by thedriver via the epicyclic gear into the hub sleeve in the forwarddirection of rotation; characterized by a second ratchet gear betweenthe brake member and the frame of the vehicle, said second ratchet gearadapted to freewheel when a torque in the backwards direction ofrotation is transmitted from the driver via the coupling sleeve, theepicyclic gear, the brake cone and the spread brake member to the hubsleeve.
 2. The hub of claim 1 wherein said lever-cone is mounted to saidframe by a brake lever.
 3. The hub of claim 2 wherein said secondratchet gear is provided between said lever-cone and said brake lever.4. A geared hub as in claim 1 or 3, characterized in that the brakemember (27)is supported to be able to shift axially towards the levercone (3) and is coupled to be unable to twist with respect to at leastone freewheeling part of the lever cone (3), which through the secondratchet gear (40, 42) can freewheel in the backwards direction ofrotation.
 5. A geared hub as in claim 3, characterized in that the levercone (3)is subdivided into an outer part (3b) which can be fixed to theframe of the vehicle by means of the brake lever (3a) and an inner part(3c) able to freewheel, and that the second ratchet gear (40, 42) isarranged between the outer and inner parts (3b, 3c) of the lever cone.6. A gear hub as in claim 3, characterized in that the lever cone (3)includes on its endface a toothed ring (42) and the brake lever (3a)includes a spring-loaded pawl mounted for engagement with said toothedring, whereby in the case of a torque acting in the forward directionthe lever cone (3) is coupled solidly to the brake lever (3a) and in thecase of a torque in the backwards direction of rotation lever cone (3)is allowed to freewheel.
 7. A geared hub as in claims 2 or 3,characterized in that the first ratchet gear is arranged between thering gear (14) of the epicyclic gear (10-14) and the inner circumferenceof the hub sleeve (4).
 8. A geared hub as in claim 1 or 3, characterizedin that the spring-loaded pawls of the first ratchet gear (15, 18) havethe same circumferential spacing (A) from one another.
 9. A geared hubas in claim 8, characterized in that the circumferential spacing (A) ofthe pawls (15c) of the first ratchet gear (15, 18) is unequal to amultiple of the pitch (t) of the associated internal teeth (18) of thefirst ratchet gear (15, 18).
 10. A geared hub as in claim 1 or 3,characterized in that the pawls (15c) of the first ratchet gear (15, 18)have spacings (A) which differ from one another.
 11. A geared hub as inclaim 10, characterized in that the pawls (15c) of the first ratchetgear have in pairs spacings which differ from one another.
 12. A gearedhub as in claim 1 or 3, characterized in that the coupling sleeve (9)for the realization of a number of forward speeds is supported to beable to shift axially on the hub axle (1) in a first position to couplethe driver (2) to the ring gear (14) and in a second position to couplethe driver to the pinion cage (10) of the epicyclic gear (10-14).
 13. Ageared hub as in claim 1 or 3, characterized in that the ring gear (14)together with the ratchet wheel (15) of the first ratchet gear can beput out of engagement with the hub sleeve by being able to shiftaxially, and that a third ratchet gear (16, 19) is arranged between thebrake cone (17) and the inner circumference of the hub sleeve (4) andserves for the transmission of the forward driving torque introduced bythe driver (2) via the pinion cage (10) into the hub sleeve (4), whenthe first ratchet gear (15, 18) is out of engagement.
 14. A geared hubas in claim 1 or 3, characterized in that the coupling sleeve (9) has afirst end fixed to rotate with the driver (2).